Sen. Kamala D. Harris, a presidential hopeful, has eagerly tried to draw distinctions with former Vice President Joseph R. Biden on policy, but she didn’t sound too interested Friday in talking about whether he’s too old for the job.

The California Democrat steered clear of taking a firm stand Friday over whether former Housing and Urban Development Secretary Julian Castro was right to play the age card against Mr. Biden in the third presidential debate.

“It is a debate, it is a debate stage, things get heated,” Ms. Harris said on CNN, adding she is more concerned with addressing what she sees as the failures of President Trump. “The focus should be on what we need to do to prosecute the case against Donald Trump.”

In the debate, Mr. Castro said what a lot of people have been thinking by questioning whether Mr. Biden was having some memory lapses on policy.